Jet pump



Patented Nov. 17, 1936 ,UNITED STATES PATENT OFFICE JET PUMP v Thomas H.Huil', Philadelphia, Pa. Application November 23, 1935,v Serial No.51,315 z claims. (ci. 23o-95) This invention relates to jet pumps, andmore particularly to jet pumps actuating atmospheric air by means ofcompressed air as driving uid. I have discovered through extensive teststhat such pumps can be considerably improved in performance byproportioning and shaping the same in a novel way, namely by positioningthe jet discharge nozzle, and thereby thel actuating jet, parallel butunsymmetrical to the surrounding pressure chamber or mixing portion oithe fluid conduit, and further by tapering or Haring the dischargenozzle itself, at least at its exit side, but better at the entranceside also.

It is accordingly the broad object of the present invention to providefor a jet pump with an improved performance, as regards the economy,eiiiciency, magnitude of pressure orsuction obtained, and range ofdifferent delivery volumes within which the performance is acceptable.

Another object of the invention is to provide for such jet pump having ajet nozzle parallel with the surrounding portion of the conduit but outof alignment with its axis.

A still other .object is to provide for such jet pump having a ilareddischarge nozzle.

It is at last an object of this invention to provide for such jet pumphaving the parts, shape, and proportions described in the specification.

These and other desirable objects and advanltagesof the presentinvention will be illustrated in the accompanying drawing and describedin the specification, a certain preferred embodiment being disclosed byway of illustration only; for since the underlying principles may beincorporated in other specific devices, it is not intended to be limitedto the one here shown except as such limitations are clearly imposed bythe appended claims.

In the drawing like numerals refer to similar parts throughouttheseveral views, in which Fig. 1 represents a longitudinal section throughthe jet pump,

Fig. 2 is a cross section on the line 2--2 of Figure 1, and

Fig. 3 is a longitudinal section through the jet nozzle of Figure 1,showing the same in an enlarged scale. y

In Figure 1 there is shown an integrally cast pump body I0 having acircular inlet 22 for the working fluid to be actuated, this fluidentering therein from the open or from a supply pipe not shown in thedrawing, and connected to the pump body in any suitable manner. Thisfluid is then conducted through a straight, round, cylindrical pressurechamber II where it passes by the nozzle I8 to be described later. Theactuated fluid passes next through the straight and round convergingcone I2, the circular cross sections of whichldiminish gradually in sizefrom that of the pressure chamber II to about one fourth to one fththereof. The fluid is then received by the straight and round divergingcone I3 with circular cross sectiors gradually increasing in size fromthat of the exit'cross section of the converging cone to a sizesubstantially equal to that of the cross-section of the pressurechamberII. It will be seen from Figure 1 that the divergent cone is much longerthan the convergent cone, about three times as long, the two conescombining to form a Venturi tube, the steepness of the conicity being inkeeping with the scientific rules of streamlining, that is to say withmore space devoted to the streamlining on the trailing side than to thestreamlining on the leading side. 'Ihe divergent cone I3 discharges theuid into a discharge pipe not shown in the drawing and connected to saidcone in any suitable manner, or the iiuid is discharged into the open,as the particular purpose may require. It is also seen from Figure 1that the conduit composed of the pressure chamber II and of the twocones I2 and I3 possesses an axis of symmetry I4, which in this case isthe axis of revolution common to the conduit portions II, I2 and I3,their walls being generated by rotation thereabout.

The actuating or driving fluid enters the pump `at the threaded inlet I5from a supply pipe not shown in the drawing. It passes through a valveI6 of any suitable construction, next through the hollow bracket I1projecting from the wall of the pressure chamber into the same, andiinally through the jet nozzle I8, from which it 'is discharged into thepressure chamber. This nozzle comprises an insert 23 screwed intobracket I1, having a straight round ared entrance conduit I9 convergentin the direction of w and a straight round conical exit portion 20gently divergent in the direction of flow, so that the diameter of thecross section common to portions I9 and 20 is smaller than both theentrance diameter of portion I9 and the exit diameter of portion 20.

The nozzle portions I9 and 20 are coaxial, and their common axis ofsymmetry 2|, or axis of revolution, is parallel to the axis of symmetryIl of the pressure chamber. According to the invention, however, the twoaxes I4 and 2I do not coincide, but they are deliberately spaced apartfrom each other, so that the nozzle I9 and 20, and

the pressure chamber ll and l2, are parallel but not concentric. I havefound that a distance between these two axes equal to about one twelfthof the pressure chamber diameter, or slightly more, leads to apronounced improvement in the performance of the pump, whicheccentricity is larger than any small accidental eccentricityunavoidable with ordinary manufacturing methods. I have also found thatone definite and fixed eccentricity takes care of a large range ofoperating conditions, and that it is not necessary to make theeccentricity adjustable, for increasing the range of good performance,at least not ordinarily. I have therefore illustrated my invention byshowing a fixed eccentricity, which is the embodiment I prefer.

The beneficial eiect of this eccentricity, manifested by experiment andtrial, can probably be explained as follows: For an efficient pumpperformance it is necessary that the actuating fluid mix with theworking fluid and flow then through the venturi in positive contact withthe walls thereof, not separated therefrom by fluid substantially atrest. A concentric jet has the tendency to flow in the latterineillcient way, but a separated eccentric jet is unstable and cannotmaintain itself, but rather makes contact with the walls on the sidenearest to it and changes then to a contacting jet.

The beneficial effect of the i'laring of the jet nozzle is believed tohave special relation to the elasticity of the actuating iiuid,compressed air. It is known in the turbine art that a ared exit nozzleis conducive to large exit velocities of elastic fluids, such as steam.I would thus have discovered that the efficiency of jet pumps isincreased by giving to the actuating jet a particularly high initialvelocity before it mixes with the working iiuid, the iiared nozzle beinga particular structure for bringing that about, and therefore of greatuse in connection with jet pumps.

I have found that the other proportions shown in the drawing are alsoimportant and should be f substantially adhered to for the preservationof the eiiiciency and performance of the pump. The distance of thenozzle exit from the entrance cross section of cone l2, and thesteepness of the two cones l2 and I3 are of importance and should not bedeparted from without assurance that such departure is not harmful. Withthe pump as shown, using air compressed to about 100 pounds per squareinch as actuating fluid, and atmospheric air as working fluid, I haveobtained a very strong air flow, and a suction up to 55 inches of water.

I claim:

1. A jet pump having a substantially cylindrical casing providing arotund conduit for receiving and discharging the pumped iiuid: saidconduit comprising a substantially cylindrical portion, a first conicalportion in conterminous relation to the cylindrical portion convergentin the direction of iiow, and a second conical portion in conterminousrelation to said first conical portion divergent in the direction offlow; jet nozzle means in said cylindrical conduit portion positioned inspaced relation to and upstream of the entrance end of said rst conicalconduit portion parallel to but out of alignment with the conduit axis;and means for supplying driving uid to the jet nozzle means.

2. In combination with a pressure supply line, a casing comprising asubstantially cylindrical conduit for receiving and discharging fluidconstricted by a pair of conical conduit portions converging towardseach other and coaxial with the conduit, and a single nozzle connectedto and receiving the entire flow from the pressure supply line, saidnozzle having its discharge tip disposed eccentrically of the conduitaxis but parallel thereto and positioned in spaced and upstream relationto the receiving end of the constricted portion of the conduit.

THOMAS Hi HUFF.

